Back in the full frame days, there were the 50mm and 35mm lenses that were the "go to" lenses. 35mm was considered wide angle and 50mm was considered normal. These focal lengths were relatively easy to design, so they gave good photo results (good image quality) at a relatively low price. Due to the film size and focal length, they also produced fairly natural looking photos, without odd distortions or optical problems.
On APSC you loose some field of view. The lens is just as good as it was before, though. So a 35mm lens is still great and gives you a lot of bang per buck, but its not a wide angle lens anymore.
Same for 50mm. Pretty cheap, great IQ, good brightness (fast aperture), but its not really "normal" in terms of field of view, so its not as versatile as it was on FF.
So the blog is probably talking about film/full frame.
But keep in mind that 35mm made for FF or 35mm made for crop will look the same on your camera! The
focal length (measured in mm, independent of camera) is not the same as
field of view (measured in degrees, after the photo is taken)! You see, the focal length is a lens property, but the field of view can be affected by the medium (the film, sensor size). On crop cameras it is cropped. Hence the name. So any 35mm lens from any manufacturer will look the same on your Pentax DSLR.
It only becomes problematic if you use a "crop" lens on a full frame, because the lens might have poor edge performance or even completely black edges (vignetting). This is because the lens makers expect that there is no film/sensor to record those edges. But! Many "crop" lenses work just fine on full frame. I think there is a thread about these on the forum somewhere. You see, calling a lens "FF" or "crop" has become a bit of a marketing buzz word.
In short, the Pentax DA 35mm f2.4, DA 35mm f2.8 macro ltd, FA 35mm f2.0, DA 50mm f1.8, DFA 50mm f2.8 macro, and FA 50mm f1.4 are all great lenses (and all are available as new). The regular DA ones are also pretty cheap. For under $500 you can buy both the DA 35mm f2.4 and DA 50mm f1.8 and you have a great kit! Very sharp lenses, good low light performance, fast AF, very compact and light, great for beginners, but they also allow you to develop your art
If you want some sample photos of the great DA 35mm f2.4, check this thread:
https://www.pentaxforums.com/forums/122-lens-clubs/196639-da35-f2-4-plastic-fantastic-club.html
If you want some really, really in-depth reviews of the various Pentax 35mm lenses, check this thread (its old, so don't post in it, but it has sample photos):
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/118765-da-3...ny-photos.html